Just wanted to provide some information that will help protect the site from hackers and annoying spammers... Very easy, and doesn't require any core hacks.
It's called GeoBlocker. It allows you to grant to deny access to the website based on countries, states / provinces, regions, zip codes / postal codes, and/or area codes.
http://xn--r1a3b.net/portfolio/GeoBlocker
Even more hardcore tip is Admin Tools from akeebabackup.com